JP2002266612A - Decompression device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively provide a decompression device for an engine positively operating by a simple structure. SOLUTION: A roller holder 29 supported pivotally around a spindle 22a and energized by a torsion spring 30 is provided with a long groove 29c in a position facing an outer circumferential face of an exhaust camshaft 25, and a roller 32 housed in the long groove 29c abuts on the outer circumferential face of the exhaust camshaft 25 and a cam slipper 27a of an exhaust rocker arm 27. When a piston is repelled and the camshaft 25 along with a crankshaft is reversed in an arrow direction in a compression stroke right before stopping of the engine, the roller 32 is moved in a left direction of the figure by a frictional force with the outer circumferential face of the exhaust camshaft 25, and the exhaust rocker arm 27 with the cam slipper 27a pushed up by the roller 32 swings clockwise and slightly opens an exhaust valve 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a valve via a valve cam and a rocker arm with a camshaft that rotates forward in conjunction with a crankshaft during operation of an engine. The present invention relates to a decompression device for an engine that holds a valve at a slightly opened position by a reverse rotation of a camshaft generated in a compression stroke.

[0002]

2. Description of the Related Art When an engine tries to reverse, an exhaust valve is forcibly opened by a decompression device to immediately stop the engine, thereby preventing an excessive load due to the reverse rotation from being applied to a starter motor or the like. Japanese Patent Laid-Open No. 4-1
It is known from US Pat. In this decompression device, a decompression cam driven by an actuator presses an exhaust rocker arm to open an exhaust valve.

In general, when the crankshaft rotates by inertia immediately before the engine stops, the piston that has received a compression load during the compression stroke cannot cross over the top dead center, and the crankshaft slightly reverses. Often stops from. Various proposals have been made to reduce the cranking load at the time of starting cranking at the next start by slightly opening the exhaust valve by utilizing the reversal phenomenon immediately before the stop of the engine.

[0004]

By the way, the conventional decompression device utilizing the reverse rotation phenomenon immediately before stopping the engine,
There is a problem that the structure is complicated and the number of parts and cost increase. Further, the decompression device in which the exhaust valve is forcibly opened by the actuator also has a problem that the cost is increased due to the necessity of the actuator.

The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a low-cost engine decompression device having a simple structure and operating reliably.

[0006]

According to the first aspect of the present invention, there is provided a cam and a rocker having a camshaft which rotates forward in conjunction with a crankshaft during operation of an engine. In a decompression device for an engine that drives a valve through an arm and holds the valve in a slightly open position due to the reversal of the camshaft that occurs during the compression stroke when the engine stops, a resilient member connects the camshaft to the camshaft. The rolling member holder urged toward, the long groove formed along the outer circumferential surface of the camshaft in the rolling member holder, and the rolling member is rollably housed in the long groove and pressed against the outer circumferential surface of the camshaft, And a rolling member having a circular cross section that can abut the cam slipper of the rocker arm,
When the camshaft rotates forward, the rolling member moves to one end of the long groove by the frictional force received from the camshaft and separates from the cam slipper, and when the camshaft rotates in the reverse direction and stops, the rolling member moves from the camshaft. A decompression device for an engine is proposed in which the rolling member moved to the other end of the long groove by the received frictional force presses the cam slipper to slightly open the valve.

According to the above configuration, when the camshaft rotates forward by the operation of the engine, the rolling member moves to one end side of the long groove and separates from the cam slipper by the frictional force received from the camshaft. The valve is opened and closed by being driven by the valve operating cam without interfering with the rolling member. When the camshaft slightly reverses and stops in the compression stroke just before the engine stops, the rolling member moved to the other end of the long groove by the frictional force received from the reversely rotating camshaft presses the cam slipper to operate the valve. Since the valve is opened slightly, the cranking load can be reduced by preventing the compression load from acting at the moment when cranking is started to start the engine next time. When the engine is started by cranking, the rolling member moves to one end of the long groove again by the frictional force received from the normally rotating camshaft, thereby preventing the rolling member and the cam slipper from interfering with each other.

Further, since the decompression device is composed of the rolling member holder urged by the resilient member and the rolling member housed in the long groove, the decompression function is ensured with an extremely simple and low-cost structure. Can be demonstrated. Moreover, since the rolling member holder is urged toward the camshaft by a resilient member, the rolling member housed in the long groove of the rolling member holder is securely pressed against the outer peripheral surface of the camshaft, and the rolling member Can be moved in the rotation direction of the camshaft.

According to the invention described in claim 2,
In addition to the configuration of claim 1, the rolling member holder is swingably supported by a support shaft, and is urged toward the camshaft by a torsion spring wound around the support shaft. An engine decompression device is proposed.

According to the above construction, the rolling member holder is swingably supported on the support shaft and urged toward the camshaft by the torsion spring wound around the support shaft. The support shaft and the urging can be reliably performed with a simple structure.

According to the third aspect of the present invention,
During operation of the engine, the camshaft that rotates forward in conjunction with the crankshaft drives the valve via the valve operating cam and rocker arm, and when the engine stops, the valve rotates due to the reverse rotation of the camshaft that occurs during the compression stroke. In a decompression device of an engine that holds the valve in a slightly opened position, the pressure is supported by the support shaft so as to be swingable, urged toward the camshaft by a resilient member, and capable of pressing the cam slipper of the rocker arm. Rolling member holder formed with a portion, a long groove formed in the rolling member holder along the outer peripheral surface of the camshaft, and a circular shape which is rollably housed in the long groove and pressed against the outer peripheral surface of the camshaft. A rolling member having a cross section, and when the camshaft rotates forward, the rolling member moves to one end side of the long groove by frictional force received from the camshaft, and the rolling member holder When the pressing portion separates from the cam slipper by being swung in one direction by the urging force of the resilient member, and when the camshaft rotates in the reverse direction and stops, the rolling member has a long groove due to the frictional force received from the camshaft. Moving to the other end side, the rolling member holder swings in the other direction against the biasing force of the resilient member, so that the pressing part presses the cam slipper and slightly opens the valve. An engine decompression device is proposed.

According to the above construction, when the camshaft rotates forward by the operation of the engine, the rolling member moves to one end side of the long groove by the frictional force received from the camshaft, and the rolling member holder is attached to the resilient member. Since the pressing portion is separated from the cam slipper by swinging in one direction by the force, the rocker arm is driven by the valve driving cam to open and close the valve without interfering with the pressing portion of the rolling member holder. When the camshaft slightly reverses and stops in the compression stroke immediately before the stop of the engine, the rolling member moves to the other end side of the long groove by the frictional force received from the reversing camshaft, and the rolling member holder is resilient. By pressing in the other direction against the urging force, the pressing part presses the cam slipper to slightly open the valve, so the next time the cranking is started to start the engine, the compression load Can be prevented from acting to reduce the cranking load. When the engine is started by cranking, the rolling member moves to one end side of the long groove again by the frictional force received from the normally rotating camshaft, swings the rolling member holder in the one direction, and the pressing portion is moved to the cam slipper. Prevent interference.

Further, since the decompression device is composed of the rolling member holder urged by the resilient member and the rolling member housed in the long groove, the decompression function is ensured with an extremely simple and low-cost structure. Can be demonstrated. Moreover, since the rolling member holder is urged toward the camshaft by a resilient member, the rolling member housed in the long groove of the rolling member holder is securely pressed against the outer peripheral surface of the camshaft, and the rolling member Can be moved in the rotation direction of the camshaft.

The boss 22a of the embodiment corresponds to the support shaft of the present invention, the roller holder 29 of the embodiment corresponds to the rolling member holder of the present invention, and the roller 32 of the embodiment corresponds to the rolling member of the present invention. , The torsion spring 30 of the embodiment corresponds to the resilient member of the present invention, and the exhaust valve 15, the exhaust cam 24 and the exhaust rocker arm 27 of the embodiment correspond to the valve, the valve cam and the rocker of the present invention, respectively. Corresponds to the arm.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

1 to 6 show a first embodiment of the present invention. FIG. 1 is a side view of a decompression device, and FIG.
FIG. 3 is a sectional view taken along line 3-3 of FIG. 1, and FIG.
5 is an enlarged sectional view taken along line 4-4 of FIG. 2, FIG. 5 is an enlarged sectional view taken along line 5-5 of FIG. 2, and FIG. 6 is an operation explanatory view corresponding to FIG.

As shown in FIGS. 1 and 2, a combustion chamber 12 and an exhaust port 13 are formed in a cylinder head 11 of a four-cycle engine, and an exhaust valve 15 for opening and closing an exhaust valve hole 14 has a stem 15a. Are slidably supported by a valve guide 16 provided on the cylinder head 11. The valve spring 17 surrounding the outer periphery of the stem 15a of the exhaust valve 15 is supported at its lower end and upper end by a spring seat 18 fixed to the cylinder head 11 and a spring seat 19 fixed to the stem 15a, respectively. The portion 15b is urged in a direction to be seated in the exhaust valve hole 14.

The exhaust cam 2 is provided between the camshaft holders 20 and 21 formed integrally with the cylinder head 11 and the camshaft caps 22 and 23 connected to the upper surfaces thereof.
4 is rotatably supported by a camshaft 25 integrally provided. The camshaft 25 is connected to the crankshaft via a timing belt, and rotates at half the rotation speed of the crankshaft. Camshaft cap 22, 2
The intermediate portion of the exhaust rocker arm 27 is swingably supported by the exhaust rocker arm shaft 26 fixed to the third arm 3.
An arc-shaped cam slipper 27a formed integrally with the exhaust rocker arm 27 abuts on the exhaust cam 24, and an adjusting screw 28 provided at the other end of the exhaust rocker arm 27 so as to be adjustable in position is provided with a stem 15a of the exhaust valve 15. Touch the top edge.

The resilience of the valve spring 17 which pushes up the exhaust valve 15 in the valve closing direction is controlled by the exhaust rocker arm 2.
7 is urged counterclockwise in FIG. 1 to push the cam slipper 27 a against the exhaust cam 24. Therefore, the camshaft 25
When the exhaust cam 24 rotates, the exhaust rocker arm 27 having a cam slipper 27a following the exhaust cam 24 reciprocates and swings, and the exhaust valve hole 14 is opened and closed by the exhaust valve 15 reciprocating following the exhaust rocker arm 27. Is done.

3 to 5, the upper portion of the roller holder 29 is pivotally supported by a boss 22a integrally projecting from one of the camshaft caps 22. The roller holder 29 includes an arm portion 29 a formed in a plate shape and pivotally supported by the boss 22 a, and the cam shaft 2.
5, a block-shaped roller support portion 29b integrally formed at the tip of an arm portion 29a extending toward the front end 5, a long groove 29c formed on the lower surface of the roller support portion 29b, and an arm portion 29.
and a stopper 29d protruding upward from the upper end of a. A torsion spring 3 supported on the outer periphery of the boss 22a
0 is the other camshaft cap 23
Are supported by the pin 31 fixed to the bracket 23a and the upper surface of the roller support portion 29b of the roller holder 29.
The roller holder 29 urged counterclockwise in FIG. 1 by the elastic force of the torsion spring 30
d stops at a position where it contacts the pin 31.

As best shown in FIG. 3, the roller supporting portion 29b of the roller holder 29 has a wall portion 29e on the side opposite to the exhaust cam 24, and the side facing the exhaust cam 24 is open. The cylindrical roller 32 accommodated in 29b is stopped at both ends by being sandwiched between the wall 29e and the exhaust cam 24. As is apparent from FIG. 4, the outer peripheral surface of the cam shaft 25 and the exhaust rocker arm 2
7, the distance from the cam slipper 27a decreases toward the left side, and the distance between the outer peripheral surface of the cam shaft 25 and the long groove 29c of the roller support portion 29b decreases toward the left side.

Next, the operation of the first embodiment of the present invention having the above configuration will be described.

In FIG. 1, when the camshaft 25 rotates clockwise during operation of the engine, the roller support 29
The roller 32 stored in the long groove 29c and pressed against the outer peripheral surface of the camshaft 25 moves to the right end of the long groove 29c by the frictional force received from the outer peripheral surface of the camshaft 25,
The roller support portion 29b is swung counterclockwise against the resilience of the torsion spring 30, and is stopped at a position where the stopper 29d contacts the pin 31. In this state, the roller 32 and the cam slipper 27 of the exhaust rocker arm 27
a, the cam slipper 27a abuts on the exhaust cam 24 without interfering with the roller 32,
The exhaust cam 24 swings the exhaust rocker arm 27 to open and close the exhaust valve 15.

Now, when the crankshaft rotates by inertia immediately before the engine stops, the piston subjected to the compression load during the compression stroke cannot cross over the top dead center, and the crankshaft slightly reverses. As shown in FIG. 4, the roller 32 is rotated by the frictional force received from the camshaft 25 which rotates in the counterclockwise direction.
Move to the left end in 9c. At this time, the camshaft 2
5, the distance between the outer circumferential surface of the roller 5 and the long groove 29c of the roller support portion 29b becomes smaller toward the left side, so that the roller support portion 29b swings clockwise against the torsion spring 30 as shown by a chain line. Move. Further, since the distance between the outer peripheral surface of the cam shaft 25 and the cam slipper 27a of the exhaust rocker arm 27 decreases toward the left side, the cam slipper 27a moves from the solid line position to the chain line position when the roller 32 moves to the left. Is pushed up slightly. As a result, as shown in FIG. 6, the exhaust rocker arm 27 swings clockwise, the exhaust valve 15 is pushed down, and a gap α is generated between the head portion 15b of the exhaust valve 15 and the exhaust valve hole 14. . In other words, with the engine stopped,
When the roller 32 moved to the left pushes up the cam slipper 27a, the exhaust valve 15 is maintained in a slightly opened state.

When cranking is performed manually or by a starter motor to start the engine, the largest force is required at the start of the cranking. Especially when the piston is in the compression stroke at the beginning of cranking,
Because the compression load of the piston is added to the cranking load,
Larger cranking loads are required. However, in this embodiment, since the exhaust valve 15 is in the open state at the moment when the cranking is started to start the engine, it is not necessary to apply a large cranking load to overcome the compression load, and the cranking is performed with a slight load. Start the ranking and start the engine smoothly.

When the engine is started, the roller 32 moves to the right end in the long groove 29c of the roller support portion 29b by the frictional force received from the outer peripheral surface of the camshaft 25.
The state automatically returns to the state shown in FIG. 1 and normal opening and closing of the exhaust valve 15 by the exhaust cam 24 and the exhaust rocker arm 27 is started.

As described above, the roller 32 supported by the roller holder 29 urged by the torsion spring 30 only comes into contact with the outer peripheral surface of the cam shaft 25 and the cam slipper 27a of the exhaust rocker arm 27. With a simple and low-cost structure, the decompression function of the engine can be reliably exhibited. In addition, the resilient force of the torsion spring 30 causes the long groove 29c of the roller support portion 29b and the camshaft 2
The roller 32 is sandwiched between the roller 32 and the outer peripheral surface of the cam 5.
It can be reliably moved within. Note that the distance between the outer peripheral surface of the camshaft 25 and the long groove 29c of the roller support portion 29b may be constant, but as the distance to the left increases as in this embodiment, the long groove 29c and the camshaft 25
Can reliably generate a surface pressure sandwiching the roller 32 with the outer peripheral surface of the roller to prevent slip.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the first embodiment, the roller 32 is brought into contact with the lower surface of the cam slipper 27a of the exhaust rocker arm 27. In the second embodiment, the roller support portion 2 of the roller holder 29 is used.
The difference is that a pressing portion 29f protruding from 9b is brought into contact with the lower surface of the cam slipper 27a.

Therefore, just before the engine stops, the camshaft 25 rotates in reverse with the crankshaft, and the frictional force received from the camshaft 25 moves the roller 32 to the left end in the long groove 29c of the roller support portion 29b. When the roller holder 29 pushed in the long groove 32c swings clockwise against the elastic force of the torsion spring 30, the exhaust rocker arm 27 pushed up by the cam slipper 27a by the pressing portion 29f of the roller holder 29. By swinging, the exhaust valve 15 can be pushed down to create a gap α between the umbrella portion 15b and the exhaust valve hole 14. In the second embodiment, the roller holder 29 swings clockwise. Therefore, it is essential that the distance between the outer peripheral surface of the camshaft 25 and the long groove 29c of the roller support portion 29b be reduced toward the left. However, since the roller 32 does not press the cam slipper 27a of the exhaust rocker arm 27, the distance between the outer peripheral surface of the cam shaft 25 and the cam slipper 27a of the exhaust rocker arm 27 does not need to be reduced toward the left.

Thus, also in the second embodiment, the roller 32 supported by the roller holder 29 urged by the torsion spring 30 is brought into contact with the outer peripheral surface of the camshaft 25,
The decompression function of the engine can be reliably exhibited with a simple and low-cost structure in which the pressing portion 29f of the roller holder 29 is brought into contact with the cam slipper 27a of the exhaust rocker arm 27.

Although the embodiments of the present invention have been described in detail, various design changes can be made in the present invention without departing from the gist thereof.

For example, in the embodiment, the decompression function is exhibited by slightly opening the exhaust valve 15, but the same function can be exhibited by opening the intake valve with a similar structure.

In the first embodiment, the roller holder 29 is pivotally supported so as to be swingable, but the roller holder 29 may be slidably guided by a guide. In particular, according to the first aspect of the invention, since the roller holder 29 does not necessarily need to swing, the guide may be linear.

A ball can be used instead of the roller 32 as the rolling member.

[0036]

As described above, according to the first aspect of the present invention, the decompression device includes the rolling member holder urged by the resilient member and the rolling member housed in the long groove. Since it is configured, the decompression function can be reliably exerted with an extremely simple and low-cost structure. Moreover, since the rolling member holder is urged toward the camshaft by a resilient member, the rolling member housed in the long groove of the rolling member holder is securely pressed against the outer peripheral surface of the camshaft, and the rolling member Can be moved in the rotation direction of the camshaft.

According to the second aspect of the present invention,
Since the rolling member holder is swingably supported on the support shaft and biased toward the camshaft by a torsion spring wound around the support shaft, the support shaft and biasing of the rolling member holder are simple. Can be performed reliably.

According to the invention described in claim 3,
Since the decompression device is composed of the rolling member holder urged by the resilient member and the rolling member housed in its long groove, it is possible to reliably demonstrate the decompression function with an extremely simple and low-cost structure. Can be. Moreover, since the rolling member holder is urged toward the camshaft by a resilient member, the rolling member housed in the long groove of the rolling member holder is securely pressed against the outer peripheral surface of the camshaft, and the rolling member Can be moved in the rotation direction of the camshaft.

[Brief description of the drawings]

FIG. 1 is a side view of a decompression device according to a first embodiment.

FIG. 2 is a view taken along line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 1;

FIG. 4 is an enlarged sectional view taken along line 4-4 of FIG. 2;

FIG. 5 is an enlarged sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is an operation explanatory view corresponding to FIG. 1;

FIG. 7 corresponds to FIG. 3 according to a second embodiment of the present invention.

[Explanation of symbols]

 15 Exhaust valve (valve) 22a Boss (support shaft) 24 Exhaust cam (valve operating cam) 25 Cam shaft 27 Exhaust rocker arm (rocker arm) 27a Cam slipper 29 Roller holder (rolling member holder) 29c Long groove 29f Pressing portion 30 Screw Spring 32 Roller (rolling member)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G016 AA06 AA19 BA18 BA31 BB09 BB17 BB21 BB25 CA02 CA04 CA06 CA09 CA21 CA23 CA25 CA27 CA29 DA13 FA36 FA38 GA01 GA07 3G018 AB05 AB16 BA17 CA09 CA10 DA10 DA15 DA29 DA30 DA32 DA83 DA85 EA21 EA21 EA33 FA03 FA17 GA03 GA11 GA14 GA18

Claims (3)

[Claims] While the engine is operating, a valve (15) is driven by a camshaft (25) that rotates forward in conjunction with a crankshaft via a valve operating cam (24) and a rocker arm (27), When the engine stops, the reversing of the camshaft (25) generated during the compression stroke holds the valve (15) in a slightly opened position. ), A long groove (29c) formed along the outer peripheral surface of the camshaft (25) in the rolling member holder (29), and a long groove (29c). And is pressed against the outer peripheral surface of the camshaft (25), and the rocker arm (2)
7) a rolling member (32) having a circular cross section capable of abutting against the cam slipper (27a), wherein when the camshaft (25) rotates forward, the frictional force received from the camshaft (25) is applied. The rolling member (32) moves to one end of the long groove (29c) to move the cam slipper (27a).
When the camshaft (25) moves away from the camshaft (25) and stops, the rolling member (32) moved to the other end of the long groove (29c) by the frictional force received from the camshaft (25)
A decompression device for an engine, wherein a valve (15) is slightly opened by pressing a cam slipper (27a). 2. The resilient member (30) is composed of a torsion spring, and a rolling member holder (29) supported swingably on a support shaft (22a) is a camshaft by the torsion spring. The engine decompression device according to claim 1, wherein the device is biased toward (25). 3. A valve (15) is driven by a camshaft (25) rotating forwardly in conjunction with a crankshaft via a valve operating cam (24) and a rocker arm (27) during operation of the engine. When the engine stops, the valve (15) is held at a slightly opened position by the reversal of the camshaft (25) generated during the compression stroke, and is swingably supported by the support shaft (22a). It is a resilient member (3
0), a rolling member holder (29) formed with a pressing portion (29f) capable of pressing the cam slipper (27a) of the rocker arm (27) while being urged toward the camshaft (25); A long groove (29c) formed in the moving member holder (29) along the outer peripheral surface of the camshaft (25), and rotatably housed in the long groove (29c) and pressed against the outer peripheral surface of the camshaft (25). Rolling member (3
When the camshaft (25) rotates forward, the rolling member (32) moves to one end side of the long groove (29c) by the frictional force received from the camshaft (25), and rolls. Member holder (29)
Swings in one direction by the biasing force of the resilient member (30), the pressing portion (29f) separates from the cam slipper (27a), and the camshaft (25) reversely rotates and stops.
The rolling member (32) moves to the other end of the long groove (29c) due to the frictional force received from the camshaft (25), and the rolling member holder (29) resists the urging force of the resilient member (30). A decompression device for an engine, wherein the valve (15) is slightly opened by the pressing portion (29f) pressing the cam slipper (27a) by swinging in the other direction.